New os-testr uses stestr under the hood, which creates .stestr but not
.testrepository directory in the current dir. Other than that, it
doesn't seem like there is any difference in the format or names of
files generated in the directory.
Change-Id: I82d52bf0ad885bd36d2f0782a7c86ac61df532f2
Closes-Bug: #1716746
Ihar Hrachyshka